Trellis coded double differentially coherent (TCD2 C) MPSK with carrier phase noise

Trellis-coded modulation over carrier-phase-noise channels is considered. Because of the difficulties in carrier-phase-tracking in these situations, demodulation techniques without the need of carrier phase tracking are preferred. One such demodulation technique is differentially coherent detection. Trellis coded modulation with differentially coherent detection gives good robustness to carrier-phase-noise at the expense of relatively low signal-to-noise ratio (SNR) gain. A differentially coherent demodulation technique, named double differentially coherent detection is presented. The SNR gain of some Ungerboeck 8-PSK codes with this demodulation technique is higher than the gain of the same codes with regular differentially coherent demodulation. This improvement is obtained at the expense of only a small decrease in robustness to carrier-phase-noise, thus improving the tradeoff between robustness to carrier-phase-noise and SNR gain